Let's be safe

On a Mac, IRCing is a safe and enjoyable experience as there
are no current exploitable ways of attacking a Macintosh
remotely via IRC, or through the the network connection
itself.

That being said, with the increasing popularity of the Mac it
is sensible to take care and exercise common sense when using
IRC, even on a Mac.

Don't accept unsolicited files

The most important rule is not to accept file transfers from
people you don't know unless you have requested the file.

These unsolicited files are almost certainly attacks targeted
against the Windows operating system, since the malicious
users don't know you are using a Mac.

Files with Windows viruses are completely harmless against a
Mac due to many different technical reasons, but you should
still not accept unsolicited files.

Avoid clicking on web page links posted by strangers

There are many websites that are set up to infect machines
with viruses and spyware. Again, these attacks are almost
certainly targeted against Windows. However, a web server run
by a malicious user can determine your chosen operating
system and potentially serve a targeted virus if an
exploitable way is found with which to attack a Mac. So,
avoid clicking on a web page link if you have any reason to
suspect the poster.

Be careful about giving out personal information

The people you talk to on IRC are strangers and you will only
gradually get to know them through their messages. Even so,
appearances can be deceiving and you are cautioned against
giving out personal information without care.

The vast majority of IRC users are decent, honest people and
many, many people have first met on IRC, and later in real
life, outside of IRC to become real friends. Still, use
caution and common sense. If someone seems too friendly, and
too interested in personal details, just disengage or put the
person on ignore.

Keep your operating system up to date

Apple frequently releases updates to the operating system to
close potential security holes. As I mentioned earlier there
are no current exploitable ways of attacking a Mac remotely
but it is reasonable to expect that one will be found in the
future.

When you are on IRC you are interacting with others and their
computers. The security updates will prevent potential future
remote attacks against your computer.

To check for updates to the operating system, go to the Apple
menu in the upper left corner of the screen, and select
"Software Update"